1. Field of the Invention
This invention relates to an engagement device in an automatic transmission, wherein a reduction ratio is automatically changed, so that the drive force of an engine is transmitted to wheels of an automobile.
2. Description of the Prior Art
Known automatic transmission, which include planetary gear units, a brake for controlling connection of a carrier of a planetary gear unit with a stationary member, and a one-way brake provided in parallel to the brake. It is customary in such a prior art automatic transmissions that a support member serving as a stationary member projects radially inwardly from the transmission housing, and an inner race and an outer race of the one-way brake are fixed to the support member and the carrier. Since the support member does not rotate, it is impossible to utilize a centrifugal force of the inner race of the one-way brake, in order to lubricate a sprag serving as a friction element of the one-way brake. For this reason, a seal ring is used for providing an oil passage, so that a lubricant of a given pressure level will be introduced from an oil pump by way of the oil passage into the sprag of the one-way brake.